remove should_use_ephemeral_cache

[sbidoul]

follow-up to #7262, towards #6852

A simple refactoring, no behavior change.

[chrahunt]

The refactoring in wheel looks good to me. Regarding the tests - do we have coverage on these cases elsewhere (like in integration tests) to ensure that we don't get unnoticed regressions?

[sbidoul]

I've been extra careful to cover all previous test cases of should_use_ephemeral_cache in the new should_build and should_cache tests. So in terms of unit tests, I'd say we'll now have a better coverage.

Regarding integration tests, I found this one that exercises caching:

pip/tests/functional/test_install.py

Lines 1179 to 1185 in 76a8954

	def test_install_builds_wheels(script, data, with_wheel):
	# We need to use a subprocess to get the right value on Windows.
	res = script.run('python', '-c', (
	'from pip._internal.utils import appdirs; '
	'print(appdirs.user_cache_dir("pip"))'
	))
	wheels_cache = os.path.join(res.stdout.rstrip('\n'), 'wheels')

I suppose there are plenty of integration tests for pip wheel and pip install that go through this part of the code.

BTW, are there instructions to run tests with coverage? I could not immediately succeed at running tox -e coverage-py3.

[chrahunt]

Not that I've found - we still need some work in this area to ensure

1. coverage execution happens in the dynamically-created venvs associated with our script fixture
2. coverage for the pip code which would have different paths between integration and unit tests gets merged

If there's not one already we can make an issue to track that activity.

[pradyunsg]

I don't think there's one for tracking that.

It's a good idea to do so, and based on my past preliminary investigation, there's support for subprocesses in coverage? Maybe we can use that?

[sbidoul]

@chrahunt tests with _builds_ in their name seem relevant.

[chrahunt]

This reads much more clearly to me, and I think we have enough coverage with our integration tests that the loss of some of the overlapping behavior expressed in the removed unit tests is OK.

[chrahunt]

Thank you as always. :)

[sbidoul]

Thank you as always

Well it's not much compared to the tremendous work you and other pip maintainers accomplish. So thank your for that, as always too :)